Method of transmitting characters



Pl'il 25, l939- w. SCHEPPMANN z-TAL v 2,156,098

METHOD OF TRANSMITTING CHARACTERS Filed July ll, 1935 Patented Apr. 25, 1939 'unirse srares ori-ica araches ivm'rnon or raANsrnrrrNe cnanncrens Damy Appiicatim .any 11, reas, serian No. sans lin Germany liuly 16, 193i 2 Claims.

It is well known to transmit characters by dissolving each character into dots which are transmitted from a sending station to a receiving station with the aid of the methods used in picture telegraphy. It is also known to make up the vtransmitting apparatus after the manner of a typewriter and to send the component parts of the respective character with the aid of storing means in the shape o discs provided with conductive segments, conductive foils, contacts and cam discs or the like, such discs being moved accordingly, as is the case with the so-called picture writers.

Further it isknown to dispense with special apparatus for synchronizing. To such end each signal that is sent is at the receiving station several times written down on the recording tape. Hereby it is attained that in the case of a departure from synchronism at least one of the character lines recorded at the receiving station shall be completai. e. readable. Ilhis method however has the disadvantage that the record lines are more or less oblique on the paper tape, in accordance with the degree of the departure from synchronism. rThis method is nevertheless suflicient in many cases. and it is so especially if the transmitted telegrams are only intended for a small circle of persons who have daily or frequently to do with these telegrama Ii however the telegrams are intended for the general public then a recording of this nature is frequently annoying, as it requires a certain skill of being read quickly.

The invention therefore has for its object to record the characters only one time and to employ a synchronizing method which shall be as simple as possible and by which on the one hand the time required for transmission shall not be\ elongated, or nearly so, While on the other hand the expenditure in apparatus on the receiving side shall be as small as possible. For this purpose the synchronizing impulses are given either in the pauses between the picture lines which serve to-compose the characters, or between the characters themselves.

The invention is described hereafter by way of example, reference being had tothe accompanying drawing in which 50. Figs. 1 and-2 are two diagrams illustrating each an' embodiment of the principle of the invention, Fig. 3 is a diagrammatic View of the receiving arrangement, Fig. 4 is a diagram relating to the operation of a glow-discharge lamp forming part of the arrangement shown in Fig. 3.

in Figs. 1 and 2 a receiving tape l and some characters A, B, C, D thereon are represented.

On the tape l shown in Fig. 1, for each picture line 2 extendingv transversely of the tape short synchronizing impulses 3 are marked. These im- 5 pulses are also given during the intervals between the characters, as will be seen from Fig. 1. Such impulses, as Will be explained hereafter, need not be recorded, Ibut the arrangement for recording them may be locked.

In the case of Fig. 2 the synchronizing impulses 4 are not given above the characters but in the interstices between the characters.

In both cases the characters are reproduced by means of seven picture lines, namely in the in- 15 terval of time tv, whereas the space ts interven= ing between the characters equals the duration of three picture lines.

In the method according to Fig. 2 three synchronizing impulses fi are given during the time t3. 20 This method has over that of Fig. 1, wherein a synchronizing impulse is given at the beginning of each picture line, the advantage that the time taken by the entire transmission may be made somewhat smaller than in the formercase. The 25 interval time t3 is given by the requisite space intervening between the characters. This time is with both methods essentially the same; in the case of Fig. 2 however the duration of the picture lines is somewhat less, since it is determined only 30v by the height of the characters so that as regards the reproduction of the characters the picture lines may follow upon each other directly.

The characters and synchronizing marks are in a well known manner preferably given by 35 means of an alternating current keyed in the signal rhythm. This has advantages in the case of a transmission by wires as Well as by wireless, because fas is well known alternating currents are easier to amplify.

The. synchronizing impulses are on the transmitting side applied to the sending cylinder or an equivalent means either directly by additional conductive elements, or a separate synchronizing impulse sender is employed. In the case of the 45 latter arrangement care must be taken that the sending'discs for the characters are not moved until the synchronizing signals are being sent. It is advantageous here to provide a frequency sender which consists of a constantly revolving contact disc with segments that .determine the synchronizing impulses. The` resultant current impulses on the one hand give synchronizing impulses to Athe receiver while on the other hand i they act to lock the l*sending discs till the synsay, the discs for sending the character signals are not released until the synchronizing impulses have been sent out. The arrangement may however be the reverse of that here described.

These two arrangements are not shown since those skilled in the art will not meet with difflculties in this respect.

The receiving arrangement represented in Fig. 3 is for the method illustrated by Fig. 2. 'I'he part thereof which preferably is to receive the transmitted characters by wireless, is shown in a purely diagrammatic manner and is designated E. The motor for the picture writer is denoted by M and the writing device proper denoted by S.

The writing device has a so-called Meyer ledge. On a cylinder this edge 6 is arranged as a helical projection. The recording of the signals is effected by means of a counter cylinder I adapted to be displaced along its axis by means of a lever 8. This action is brought about with the aid of a relay Il. The arriving impulses displace'the cylinder 1 slightly along its axis. Herebythe signal is printed on the paper tape I. Instead of this writing device a writing device of another type may of course beemployed. The details thereof are immaterial to the idea of the invention. y

One of the output terminals of the receiver is continuously connected with the synchronizing device as well as with the writing device. other terminal however is in dependency upon the position of the receiving arrangement connected alternately to the writing device and to the synchronizing arrangement. This is effected in such a manner that whenever synchronizing signals are arriving from the transmitter the synchronizing ldevice is cut in. After the synchronizing signals have ceased the writing device is cut in and remains in this condition until synchronizing signals-Will arrive again. This change is by no means accomplished by the signals arriving from the transmitting side but is effected by the receiving arrangement, as will be more fully explained hereafter. For this purpose the terminal III of the receiver is in connection with the brush IIB of a distributor. This brush is driven by the motor shaft vthrough a translating gearing I2, I3. Such translation is necessary as the intervals of time t3 and t7 differ from each other. The distributor besides has stationary conductive segments IB and I5. Segment I4 is attached to the writing device while segment I5 is .in connection with the synchronizing device.

The motor M has a coarse regulation not shown in the drawing. The well known centrifugal governors may be used here. The lmotor* M must tend to be too quick or too slow while the synchronizing device has for its object to retard or to accelerate it on each synchronization. Ar-

rangements of this type have already beenproposed for other purposes. In the following, however, according to the further invention an arrangement is describedy which is especially adapted for the purpose and which responds safely to the extremely short synchronizing impulses.

The segment I5 of the distributor is connected with a rectifier IB, as is necessary if, as mentioned Thev herebefore, the picture signals or synchronizing signals are given as a keyed alternating current. Fastened on the motor shaft is a cam disc I1 which is to actuate a contact lever I8. 'This lever is to cooperate with contacts I9 and 20. The disc I1 to such end has a cam portion 2| and a recess 22. Lever I8 is actuated by a pin or the like 23, as is indicated by an arrow. The regulation is Iaccomplished by inuencing the field winding 24 of the motor M. This winding is connected in series with a regulating resistance 25 and a voltage source 28. The regulation is made by shortcircuiting the resistance 25 with the aid of relay 21. It may also be thought that the relay 21 might be actuated directly by the described contact arrangement I'I to 23, but as stated an arrangement is provided that acts to elongate the extremely short synchronizing impulses.` Such elongation is performed with the aid of the glowdischarge lamp 28. Thislamp is connected in series with the relay 21. and two resistances 29, 30 and to the voltage source 3| The operation is as follows:

Let it be assumed that the glow-discharge`v lamp 28 is in operation. The contact device intended for synchronizing now has at iirst to extinguish the lamp 28. This is accomplished by the contactlever I8 applying over contact 20 and with the aid of the voltage source 32 a counter voltage to the lamp 28. The current source 3| is not able to reignite the lamp 28 since it only supplies the operation voltage to the lamp not however the ignition voltage which is considerably higher than this. The cam disc I1 continues to move so as to close the circuit over the contact I9. As soon as a synchronizing signal arrives in the receiver an additional voltage is applied hereby to the resistance 29 so that the lamp 28 is ignited. When the extremely short synchronizing impulse has ceased the lamp 28 remains in operation as the voltage source 3l is supplying the requisite energy. The cam disc I 1 then again acts to disconnect the lamp 2B as will appear from the foregoing.

In Fig. 4 the operating conditions of the lamp 28 are shown. The potentials have been plotted in dependence upon time. At the instant tz the lamp is ignited, at the instant tb the synchronizing signal detected by the receiver ceases, the

instantt1, i. e. the instant when it is again extinguished by the contact device. The instant tz thus is determined by the arrival of the synchronizing signal while the instant t1 is determined by the contact device controlled on the receiving side. According to the degree of departure from synchronism the-time T will be longer or shorter or the eld circuit of the motor will be regulated a longer or shorter time.`

`Instead of the distributor device or contact arrangement here shown other arrangements may of course be disposed. For instance it is possible to construct the distributor in using spring sets operated by a cam disc or the like. The same applies for the contact device I1 to 23. l

During the time not used for synchronizing the magnet 9 is cut in, and the writing device then can receive the signals which serve for composing the characters.

' the signs, using a continuously operating variable speed dir ect current motor at the receiver, a glow l discharge lamp connected to a voltage source,

and means driven by the motor for recording the signs, the method comprising normally maintaining said motor speed at a predetermined value, sending synchronizing impulses in the interval between the transmission of said picture impulses, and changing said motor speed to approach a diierent predetermined value in response to the received synchronizing impulses, characterized in changing the speedV of the motor for an interval dependent upon the departure from synchromsm of said motor by causing said synchronizing impulses to ignite said glow discharge tube.

2. In a system for transmitting written signs by transmitting a series of short picture impulses which when received build up a representation of the signs, using a continuously operating variable speed direct current motor at the receiver, a glow discharge lamp connected to a voltage source, and meansdriven by the motor for recording the signs, the method comprising normally maintaining said motor speed at a predetermined value,

sending synchronizing impulses in the interval between the transmission of said picture impulses, and changing said motor speed to approach a different predetermined value in response to the received synchronizing impulses, characterized in changing the speed of the motor for an interval dependent upon the departure from synchronism of said motor by causing said synchronizing impulses to ignite said glow discharge tube,`

and extinguishing'said lamp after said interval has elapsed.

WILHELM SCHEPPMANN. CHRISTIAN WISSPEINTN'ER. 

